Switchboard



(N0 Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD.

No. 592,330. Patented Oct. 26,1897.

1 l/VE L INC No. 2

I rwcnzr Ail/0 6. Keflgy by his ad'orlceyg UNTTED STATES PATENT EEICE.

.lI'lLO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGGS\VITCI'IBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent N0. 592,330, dated. October26, 1897.

Application filed December 11, 1889. Serial No. 333,343. (No model.)

To all whom it may concern:

Be it known that I, MILO G. KELLOGG, of Chicago,1llinois,temporarilyresiding at Stuttgart,in the Empire of Germany,have invented certain newand useful Improvements in Mul tiple Switchboards forTelephoneExchanges, of which the following is a full, clear, concise,and exact description, reference being had to the accompanying drawing,forming a part of this specification.

My invention relates to lines which are normally grounded at the centraloffice.

It consists, first, of an improved system of subscribers calling on suchlines; secondly, to an improved system of testing such lines, and,thirdly, to an improved night-signal at the central office.

In the drawing accompanying this specification, showing my invention,the figure illustrates the apparatus and circuits in which I prefer toembody my invention.

The subscribers lines in the exchange are divided among the differentboards of the exchange as in the usual manner, as many boards beingemployed as the size of the exchange requires. On each board is aspringjack or similar switch for each line. Each switch has aspring-contact normally bearing upon an insulated contact-anvil and athird contact-piece insulated from the rest except by the circuitconnections. A subscribers line is traced through these spring-jacks asfollows: from ground at G through two branches in parallel, one branchincluding a call-generator 1, bells 2, and terminating in a contact 6,normally or when the telephone is not switched for use, in connectionwith the lever 4, the other branch including the operators telephone set3 and terminating in a contact 5, in connection with the lever 4 whilethe telephone is switched for use, thence over the subscribers lineconductor S, through the test-contacts j in the jack-switch at eachboard, thence through the pairs of normally closed contacts 9 h, theannunciator A, the normally closed pair of contacts 19 q, opened whilethe annunciator indicates a call, to the common conductor 0,grounding-switch s, which is grounded directly or through the relay 1",according to whether the switch rests upon the contact 5 or s.

The construction of the line-annunciator Ais shown more in detail inline No. 2. The line conductor S, after passing through thespring-jacks, is connected to the bolt 0 and thence through the coil ofthe annunciator to the spring 19, mounted upon the metal frame 0. Thespring 19 normally bears against the contact g, which is mounted uponthe frame 0 by means of the bolt 0*, both of which are insulated fromsaid frame. To this bolt 0 is connected the common grounding-wire C.During the daytime, or while the exchange is active, this grounding-wirehas its circuit closed through the circuit of switch 3 and contact 8 toground at G.

At each board is an operators test outfit, comprising a plug T, a testreceiving instrument S, a test-battery B, all of which are grounded atG. The order of these elements is immaterial as long as the battery andtest receiving instrument are between the testplug and ground. One ofthe outfits is provided at each board.

At board A is shown one of the switching sets, there being as manyswitching sets at each board as there are connections to be establishedat the time of greatest activity. A switching set comprises two plugs DD, connected together by a flexible cord conductor 01, in the circuit ofwhich there is a looping-in switch Y,which introduces a telephone t, acall generator or battery B, or a clearing-out annunciator o, accordingto whether the switch Y rests upon the contacts 8 s, r r, or q q. Theswitch Y normally rests upon the annunciator-contacts q q. Theannunciator o is individual to each set, but the call-generator B andoperators telephone set i are used in common with a number of switchingsets in the manner well known to electrical engineers.

The plugs are composed of a body of insulating material m, upon whichare mounted contacts 92 so arranged as to make contact with the metallicgrounded plate 0, upon which the plugs normally rest,and to be inconnection with either of the contactsg orj when inserted into the holeZ of a spring-jack a.

When both plugs are inserted in s'pring-jacks, their circuit iscompleted over two line-wires connected to the jacks. When one plug onlyis inserted in a jack, the circuit of the other plug is completed toground at G through the metallic supporting-plate 0.

The strength of the test-batteries is so adjusted to the resistance ofthe subscribers apparatus or his line conductor, or both, that when inits circuit and in circuit with it alone the test receiving instrumentswill not respond. If, however, the pairs of contacts gh of the jacks andthe pairs 01": contacts 19 q of the line-annunciator are closed, twobranches to ground are provided for the test-batteries, the jointresistance of which permit the test receiving instrument to respond.This circuit may be traced as follows: from ground at G, test receivinginstrument S at board 2, battery B, test-plug T, test-contact j,testconductor S thence in parallel over two grounded wires or branches,one branch being traced over the line-circuit S to ground at thesubscribers station, the other branch being traced over theconductorS,through the pairs of contacts 9 h in the jacks at the severalboards, through the line-annunciator A, the pair of contacts 19 q,controlled by said a11- n-unciator, common grounded wire (3, thence toground at G by way of either the contacts s or 8 two branches of thetest-circuit permits the test-battery to cause the test receivinginstrument to respond and therebyindicate that the line is free.

At board A is shown a test outfit testing a busy line. The otfice groundwas first cut off by the opening of the contacts 19 q, caused by thefalling flap of the annunciator. This alone prevents the test receivinginstrument from responding. serts her switch-plug D into jack a, asshown, thereby lifting the spring-contact g from its anvil h, openingthe office ground at a second point. The opening of this pair ofcontacts alone prevents the response of the test outfit.

It will be noticed that the line conductor S is connected temporarily tothe office ground as follows: spring-contact g, plug-contact n, cordconductor cl, including the operators telephone set i, contact n of theplug D, and grounded plate 0.

. phone set If is so great that-the test receiving from responding atest of two connected lines To facili- 'tate these adjustments, theresistance to indicates that they arebusy.

ground through the subscribers station may be high'and the offiee groundthrough the annunciator may be comparatively low. The

I existence of the annunciator branch to ground The joint resistance ofthese terns in that the line tests busy whether it The operator atboard2 in- The resistance of the teleis an established test-circuit, andthis branch ;sends in a call, a current energizes the relay r and closesthe pair of contacts 7, permitting the battery B to act upon anindicator 1 2, indicating to the night operator that a call has beensent in at board 2. There is one of 5 these relays r individual to eachboard of the :exchange, or, in other words, there is a different commonwire 0, a different switch .9,

and a different relay 4" for each board.

The indicators 2 9 10, &c., are grouped at a night station or table,where they may be overlooked by the night operator. I The noise of thefalling flap alone may be snfficient to attract the operators attention,ora signal in addition of the ordinary kind may be given in the usualway. The switch 5 connected to the common wire 0 by broken lines,controls a modification by which a direct'ground or a, groundednight-indicator 2 may be intro- 3 duced into the circuit, according towhether ithe switch rests upon the contact 8 or is switched or whetherits annunciator indi-" This system of testing differs from othersyscates a call, and it is applicable in its general features to allsystems of testing in which the test is made directly to the circuit ofthe line,

whether the line is switched or not, and in ,which the test indicateswhether or not the iconnection of the line is broken to the office 5ground.

The relays r should preferably be of comi paratively small resistanceand of a construc- ,tion which will cause them to operate when itheusual calling current is sent through them. The current of a subscribersgenerator being a comparatively strong one and genierally one rapidlyintermittent frequently icauses induction on neighboring wires,whichimpedes telephone conversation on them as long as the subscriber maythink it necessary or find it convenient to operate his generator inmaking a call.

In this system the circuit is open as soon as a call is indicated, sothat ;further operation of the generator will not .own signal-bell willstop cause prolonged induction on neighboring lwires.

At the same time the subscribers ringing as soon as j his annunciator atthe central office indicates a call, and he thereby knows that his callhas been indicated.

In telephone-exchanges sign al-bells are not an operator stationed ateach board to watch the annunciator indications and answer the calls,and the operation of the annunciators themselves generally make a soundwhich is heard for a short distance. At night, however, one operator isfrequently sufficient to attend to the calls on many boards; butit isimpossible for her to watch closely all the drops at the variousboards-to see when a call is indicated. To remedy this trouble, I placerelays or annunciators, as described, in the common circuit of eachboard or group of lines, and I group the annunciators, one operated byeach relay, at a night-table, where the operator may remain to watch theindications while she is not at the switchboards answering calls. Theannunciators at the night board indicate the board or group of linesfrom which the call comes, and on going to the board she sees whatparticular line has made the call.

I am aware that heretofore it has been proposed to divide the lines ofan exchange into groups and place a telephone in a wire common to thegroup; but in such systems the telephone is placed where the operator islocated to make the connections for the group of lines. Signal-bells orannunciator-s have also been employed in the same way in a wire commonto a group of lines. It has also been proposed to provide all theindividual annunciators of an exchange with contacts to close thecircuit of a signal-bell common to all of them when an annunciator isoperated by a calling subscriber. The operator is thus informed that acall has been made some where in the exchange, but he must search allthe groups or boards to ascertain the annunciator of the line indicatingthe call.

In my system the annunciator-s common to the respective groups of linesare located at a table where the night operator of an exchange is toremain, and the line-annunciator of each line is located at theswitchboard where its calls are to be answered. Thus the groupannunciator or indicating device indicates to the night operator thegroup of lines in which a call has been sent in, and on going to theswitchboard of the group he readily finds the individual annunciator ofthe line that has called.

In my system I have an individual annunciator in each line and also onefor each group of lines, and each subscriber has a generator foroperating both annunciators, and when a subscriber operates hisgenerator to call both annunciators are operated, one indicating to theoperator the group and the other the particular line of the group.

I claim as inyinvention and desire to secure by Letters Patent- 1. In amultiple-switchboard exchange, a test-circuit, normally closed contactsin said test-circuit, and a call device opening said contacts whileindicating a call.

2. In a multipleswitchboard exchange, a test-circuit, normally closedcontacts in said test-circuit, an annunciator in said test-cireuitopening said contacts while indicating a call.

3. In a multiple-switehboard exchange, three parallel circuits, onecontaining normally closed contacts, the second containing thesubscribers line, and a third normally open and closed for testing,containing a test receiving instrument and battery so adjusted to eachother and to the two other parallel circuits as to give one indicationwhile the normally closed cont-acts are closed, and another indicationwhile they are open; in combination with a call device opening contactswhile indicating a call. I

4. In a multiple-switchboard exchange, a test-circu it, comprising atest outfit,connected on one side to ground and on the other side to aline conductor grounded at both ends; in combination with acircuit-breaker in one grounded end, said test outfit being adjusted togive one indication while the circuitbreaker is closed, and anotherindication while the circuit-breaker is open, and an annunciator openingsaid circuit-breaker.

5. In a multiple-switchboard exchange, a telephone-line comprising inthe order named, a subscribers grounded line, test-contacts, one at eachboard and an office grounded connection containing normally closedcontacts; in combination with a grounded test outfit at each boardadapted to be connected to a testcontact for testing, so adjusted to theresistance of two grounded ends as to respond while the said contactsare closed but to fail to respond when they are open, and an annunciatoropening said contacts while indicating a call.

6. In a multiple-switchboard exchange, a grounded telephone-linecomprising in the order named, a subscribers line, test-contacts, one ateach board, normally closed jack-contacts, a pair at each board, and aground connection containing normally closed annunciator-eontacts; incombination with a test outfit at each board adapted to be eonnected toa test-contact for testing, so adj usted to the resistances of thegrounded ends of the telephone-line as to respond when theannunciator-contacts and the jack-contacts are closed, but to fail torespond when any of the said contacts are opened, an annunciator openingsaid annunciator-contacts while indicating a call, and a switch-plugadapted to open a pair of jack-contacts while the line is switched foruse. I

7. In a telephone-exchange system, two or more groups of lines, anindicating device or annunciator for each group common to all the linesof that group, such indicating devices for all the groups being arrangedtogether at the central office, an individual annunciator for each linelocated at the board where its calls are to be answered, and a generatoror source of electricity at each subscribers station for causing theoperation of the individual annunciator of the line and the indicatingdevice of the group to which the line belongs.

8. In a telephone-exchange system, two or more groups of lines, anindicating device or annunciator for each group common to all the linesof that group, such indicating devices for all the groups being arrangedtogether at the central oflice, an individual annunciator for each linelocated at the board Where its calls are to be answered, a generator orsource of electricity at each subscribers station for causing theoperation of the individual annunciator of the line and the indicatingdevice of the group to which the line belongs, and a switch fordisconnecting each group of lines from its common indicating device.

9. In a telephone-exchange system, groups of lines each line passingthrough its switchboard system and an individual annunciator and thelines" of a group then uniting into a common Wire or circuit for saidgroup, in combination with a relay in the common Wire or circuit and anindicator or annunciator controlled by said relay to indicate when acall has been made on any'line of its group, the individual annunciatorof each line being located at a board of the exchange Where its callsare to be answered, and the indicators of the different groups of linesbeing arranged together at the central office, substantially as setforth.

MILO G. KELLOGG.

NVitnesses:

FRANCES D. KELLOGG, MARGARETHA RIEHL.

